Am I limited to using primitive objects to create shapes in Blender or can I 'sketch' a freeform shape?
How to (sort of) do a CAD sketch in blender:

Add a single vertex. This can be done by deleting all the other vertices in the default cube, or enable the &quot;Extra Objects&quot; addon an press ShiftA and choose &quot;Single Vert&quot;.
With the vertice selected go into edit mode and orthographic view from the desired side.
Press E to extend into the shape you want. It will create a bunch of points in the shape you like.
When you want to close off a shape, select the two vertices you want to connect and press F to automatically join them, in this case with an edge.
Now fill in the shape. Select something to fill in and press F to automatically join them, this time with a face.
Now select everything (or something), and press E to extrude them into the desired height.